The art has been seeking an acceptable non-azide gas generant which has the desired combination of properties for being a drop-in replacement for the conventional sodium azide-fueled gas generating composition used in air bags in passenger vehicles.
In addition to properties, such as acceptable rate of gas generation and reduced or no toxic combustion byproducts, a proposed replacement for the conventional sodium azide-fueled gas generant must be capable of being manufactured and formed into a pill, pellet, extruded cylinder, or other desired shape charge. The desired shape, typically a pellet, must be capable of retaining structural integrity.
Various methods have heretofore been proposed for processing gas generant compositions to obtain shaped charges such as pellets. However, different gas generant compositions behave differently during the pelletizing process, and particular process conditions suitable for fabricating objects composed of one gas generant are not necessarily applicable to processing or fabricating objects, such as pellets, composed of a different gas generant composition.
We have proposed a non-azide-fueled gas generant composition, and have made extensive studies on its preparation and fabrication. We have developed certain techniques for fabricating the non-azide composition into pellets or other desired forms. In the course of that work, we observed, however, that attempts to pelletize directly anhydrous gas generants based on a fuel of the tetrazole class, such as aminotetrazole or bistetrazoleamine, produces pellets that crumble and lose their pellet shape within 24 hours at Rh 45% at 25.degree. C.
As a result of such efforts, we have determined that it would, therefore, be a significant advancement in the art to provide a method for preparing shaped charges, such as pellets, comprised of non-azide tetrazole-fueled compositions directly from an anhydrous material composed of that composition wherein the shaped charges so produced retain their structural integrity after exposure at a Rh 45% at 25.degree. C. It would be an advancement in the art to provide shaped forms, such as pellets or the like, which are capable of being combusted to generate large quantities of gas that would overcome the problems identified in the existing art. It would be a further advancement to prepare shaped charges, such as a pellets, comprised of non-azide tetrazole-fueled gas generating compositions which are based on substantially nontoxic starting materials and which produce substantially nontoxic reaction products. It would be, in particular, an advancement in the art to produce combustion gases which primarily consist of nitrogen, with lesser amounts of carbon dioxide and water vapor so as not to exceed allowable occupant exposure standards for carbon dioxide and carbon monoxide. It would be another advancement in the art to prepare shaped charges, such as pellets, comprised of gas generating compositions which combust to produce limited particulate debris and limited undesirable gaseous products. It would also be an advancement in the art to prepare pellets comprised of gas generating compositions which combust and form a readily filterable solid slag upon reaction.
Methods for making shaped charges, such as pellets, directly from anhydrous non-azide tetrazole-fueled gas generant compositions are disclosed and claimed herein.